Lubricants, such as lubricating oils and greases, are subject to oxidative deterioration at elevated temperatures or upon prolonged exposure to the elements. Such deterioration is evidenced, in many instances, by an increase in acidity and in viscosity, and when the deterioration is severe enough, it can cause metal parts to corrode. Additionally, severe oxidation leads to a loss of lubrication properties, and in especially severe cases this may cause complete breakdown of the device being lubricated.
Antioxidants or oxidation inhibitors are used to minimize the effects of oil deterioration that occur when hot oil is contacted with air. The degree and rate of oxidation will depend on temperature, air and oil flow rates and, of particular importance, on the presence of metals that may catalytically promote oxidation.
Water (moisture) is another critical problem. In spite of even extraordinary precautionary efforts water is found as a film or in minute droplets in vessels containing various hydrocarbon distillates. This brings about ideal conditions for corrosion and damage of metal surfaces of the vessels and the materials contained therein. Also in the lubrication of internal combustion engines quantities of water are often present as a separate phase within the lubricating system. Another serious problem in respect to metallic surfaces in contact with adjacent metallic surfaces is the surface wear caused by the contact of such surfaces. One material capable of simultaneously effectively coping with such problems as these is highly desireous.
The use of sulfur-containing compositions such as sulfurized isobutylenes has been well known for their antiwear properties in a variety of lubricant applications as exemplified by U.S. Pat. Nos. 3,703,504; 3,703,505, and 3,873,454. It has now been found that sulfur-coupled hydrocarbyl derived mercaptobenzothiazole adducts provide exceptional multifunctional antiwear, antioxidant and friction reducing properties. These remarkable benefits are to be expected for a variety of synthetic and mineral oil based lubricants and also for liquid hydrocarbon fuels.
To the best of our knowledge, these compositions have not been previously used as multifunctional additives in lubricating oils, greases, or fuel applications. The additive products themselves and lubricant compositions thereof are both believed to be novel.